The configuration of a "reverse loop" generates a magnetic field that applies a force in an opposite direction of a movable contact mechanism of a circuit breaker. Under "short circuit" or "tripping" conditions, large currents pass through the reverse loop, and accordingly, the magnetic field which applies a force on the movable contact mechanism causes the circuit breaker to trip by applying a force which is greater than the force of the movable contact mechanism.
Generally, and in order to enhance the electromagnetic force of the reverse loop, a magnetic flux concentrator, usually in the form of a steel block, is positioned within the partially looped portion of the conductive path of a reverse loop.
The steel block shunts another magnetic field and accordingly its force that is opposite to the magnetic field that applies a force in a direction opposite to a force that maintains the movable contact mechanism in a closed or current carrying configuration. Therefore, the placement of a magnetic flux concentrator within the reverse loop enhances the magnetic field that causes the circuit breaker to trip in overload situations.
Since a magnetic field can only penetrate a limited distance into the steel block, the "skin effect" of the steel block limits the effectiveness of the shunt.
The placement of the magnetic flux concentrator requires the implementation of at least one insulating buffer zone positioned between the magnetic flux concentrator and a portion of the reverse loop. This buffer zone prevents the short circuit of the reverse loop.
U.S. Pat. No. 5,313,180 entitled Molded Case Circuit Breaker Contact, describes a rotary circuit breaker. This patent describes the use of an anvil formed from a rigid metal block. The anvil is positioned in between the two strands of a current input conductor or "reverse loop" and makes contact with one of the strands to receive impact forces from the movable contact as it strikes the stationary contact positioned on the strand making contact with the anvil.